In recent years, manufacturers have redesigned tow trucks and associated attachment apparatus used to tow vehicles. Now, instead of towing a vehicle by its frame and bumper, a vehicle is towed by its wheels. Such assemblies are generally referred to as wheel lift towing attachment assemblies because the assembly lifts a vehicle by its wheels rather than by the vehicles body structure.
An example of a wheel lift towing device can be found in U.S. Pat. No. 4,637,623 issued to Bubik on Jan. 20, 1987. The '623 Bubik patent discloses a wheel lift attachment assembly having a telescoping boom extending rearwardly from a tow truck chassis. The boom fixedly positions a support structure having a transverse wheel support beam below the vehicle to be towed. Two wheel support members are mounted adjacent to opposite ends of the support beam and include a elongated arm extending generally transverse to the axis of the support beam and a wheel retainer mounted on the end of the arm. Pivotal collars are pivotably mounted atop of the support beams and adjacent to the opposing ends thereof. The collars provide horizontal and vertical movement relative to the fixed support beam for positioning the wheel support members for receiving the wheels of the vehicle to be towed. The pivotal collars as disclosed in the '623 Bubik patent have a tapered passageway for slidably receiving the wheel support members. The tapered passageway allows the wheel support members to be vertically disposed relative to the support beam; that is, tilted within the tapered passageway. A pin extends vertically upward from the collar into the tapered passageway for engaging the wheel support members to prevent the wheel support members from sliding horizontally within the passageway. A second pin is provided for engaging the wheel support members to prevent the wheel support members from vertically tilting within the passageway. The wheel support members are tiltible between a first position wherein the first pin engages the wheel support members to prevent the wheel support members from sliding horizontally within the tapered passageway, and a second position wherein the wheel support members are free to slide horizontally within the tapered passageway.
The '623 Bubik patent does not disclose a collar having an upper plate and lower plate spaced vertically below and laterally offset from the upper plate wherein the upper and lower plates form a channel having a constant vertical dimension (i.e. not tapered) within which the wheel support members can slide horizontally and tilt vertically. Also, the '623 Bubik patent does not disclose collars positioned at the ends of the support beam such that the wheel support member lies below the top of the support beam when in use. Instead, the Bubik '623 patent discloses a collar which is positioned on top of the top of the support beam and thus the wheel support members lie above the top of the support beams when in use. Finally, the '623 Bubik patent does not disclose a pin to be used in conjunction with the upper and lower plates wherein the pin is positioned vertically below the upper plate and parallel with the lower plate. A pin positioned in such a manner prevents the wheel support arm from vertically tilting away from the upper and lower plates without extending through or into the support arm. Thus, the wheel support arm is positioned between the pin and the upper plate.
An advertisement published by Century.RTM. discloses a wheel lift attachment assembly comprising a support beam having wheel abutments telescopingly coupled to each end of the beam. The advertisement also discloses L-shaped wheel support arms coupled to the end of the wheel abutments by means of a collar. The collar is rotatably coupled to the ends of the wheel abutments to provide horizontal rotation of the support arms relative to the ends of the wheel abutments. The collar includes an upper plate and a lower plate spaced vertically below and laterally offset from the upper plate to form a channel having a constant dimensional shape for slidably receiving the support arms. The collar allows horizontal positioning of the support arms with respect to the support beam and vertical positioning between the plates. In other words, the support arms can be both vertically tilted and horizontally slid within the channel formed by the upper and lower plates in addition to the horizontal rotation about the ends of the wheel abutments. The Century.RTM. advertisement discloses a single pin extending from the collar which extends through one side of the support arm to prevent the arm from being horizontally slid and vertically tilted within the channel. Additionally, the upper plate of the rotatable collar lies in a plane above the top surface of the support beam such that nearly all of the support arm lies above the top of the support beam when the support arm is disposed between the upper and lower plates and parallel therewith.